Object Name: Messier 88
Alternative Designations: M88, NGC 4501
Object Type: Type Sc Spiral Galaxy
Constellation: Coma Berenices
Right Ascension: 12 : 32.0 (h:m)
Declination: +14 : 25 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 9.6 (mag)
Apparent Dimension: 7×4 (arc min)
Locating Messier 88: Begin with the base M84/M86 pairing located almost exactly mid-way between Beta Leonis (Denebola) and Epsilon Virginis (Vindemiatrix). The above map shows quite some distance between the galaxies, but by running a “grid” pattern, you can starhop the Virgo galaxy field with ease. Once you have M84/M86 in sight, move one low power eyepiece field east and hop north less than and eyepiece field for M87. Now you understand how Charles Messier ran his sky patterns! Continue north for 1 or two eyepiece fields and then shift east by one. This should bring you to M88. Because not all eyepieces have the same apparent field of view, these dimensions may be slightly more or less – but you’ll soon understand the “grid” mentality. In a small telescope, M88 will appear as a vague, round misty patch. In larger aperture, you will see several smaller, fainter galaxies along the way, but M88 will be far brighter and larger than any others in the field – appearing round with a brighter center. Once located, add a bit more magnification to darken the background field and bring out details. Because M88 is close to magnitude 10, it will require dark skies to be seen with ease.
What You Are Looking At: Uncurling its spiral arms across 130,000 light years of space, Messier 88 is a non-barred Seyfert Galaxy which contains a whole lot of gas. Even though a Seyfert is a starburst galaxy, the neutral interstellar medium contained within it can play a very important role on how quickly new stars form. ” It is known that NGC 4501 has high degree of central gas concentration for a non-barred galaxy. The CO major features (1) a nuclear concentration which is resolved into double peaks, (2) spiral arms. The feature (1) has a low star-forming efficiency, which might be due to low Mgas/Mdyn ratio. Double peaks are located on the root of optical spiral arms in a HST image.” says S. Onodera (et al). “To understand gas motions in NGC 4501, we did model calculations of gas cloud orbits governed by a stellar spiral potential, which is a modification of the model with a bar potential. The observed CO spirals and non-circular motions were explained with this spiral model. We estimated the loss of angular momentum due to galactic spiral shocks in orbit crowding regions and gravitational torques exerted by the stellar spirals. We found that the galactic shock is dominant. These mechanisms lead to gas inflow and possibly explain the central-condensed double peaks in NGC 4501.”
Yep. That’s right. M88 might be doubling its nucleus! “The solar magnesium-to-iron ratios in the galactic nuclei show evidence for long duration of the secondary nuclear star formation bursts that produced the chemically distinct stellar subsystems.” says O.K. Sil’chenko (et al). “Detailed morphological and kinematic analyses made for the stellar and gaseous structures in the centers of NGC 4216 and 4501 have revealed the presence of circumnuclear stellar-gaseous disks with radii of some hundreds of parsecs that demonstrate fast axisymmetric rotation and lie exactly in the planes of the main galactic disks.”
So, if stars in Seyfert galaxies form along the bars and M88 is either just doubling its nucleus or beginning bar formation – where do the stars in this starburst galaxy begin? Try in the dusty arms! “Since at rest wavelength (i.e., in nearby galaxies) the NIR light also traces a relatively old stellar population, NIR imaging is the technique of choice to observe the “stellar backbone” of galaxies: the old stellar population which, by assumption of a mass-to-light (M/L) ratio, will give an estimate of the mass. We imaged a complete sample of 57 galaxies with INGRID for this reason: to study the old stellar component, not affected by dust extinction. In one of the lines of our overall project, the INGRID Ks imaging will be compared with B and R broad- band images, as well as with narrow-band H? images which trace young, massive stars and current star formation. This comparison can indicate how mass and star formation are concentrated in spiral arms, and why they are concentrated to a different degree.” says J. H. Knapen (et al). “About 75% of all disk galaxies have bars where stars move on elongated periodic orbits and thus support a non-axisymmetric potential. Gas in bars shocks and loses angular momentum, which implies that bars form a mechanism to transport material inward in a rotationally supported galactic disk. This explains why bars are relevant for questions related to the origin, evolution, and maintenance of stellar and non-stellar activity in or around the nuclei of galaxies: massive black holes, AGN or (circum)nuclear starbursts all need fuel to maintain their activity and whereas enough gas is available in the disk at large, moving this gas inwards implies making it lose a considerable amount of angular momentum.”
History: M88 was discovered by Charles Messier on the night of March 18, along with 7 other member galaxies of the Virgo Cluster. In his notes he writes: “Nebula without star, in Virgo, between two small stars & one star of the sixth magnitude, which appear at the same time as the nebula in the field of the telescope. Its luminosity is one of the faintest, and [it] resembles the one reported in Virgo, No. 58.”
William Herschel would also observe M88 as would his son John, Lord Rosse identified it as one of the first “spiral nebula”, but it was Admiral Smyth who gave it the attention it deserved: “A long elliptical nebula, on the outer side of Virgo’s left wing. It is pale-white in color, and trends in a line bearing np [NW] to sf [SE]; and with its attendant stars, forms a pretty pageant. The lower or northern part in the inverted field is brighter than the southern, a circumstance which, with its spindle figure, opens a large field for conjecture. This is a wonderful nebulous region, and the diffused matter occupies an extensive space, in which several of the finest objects of Messier and the Herschels will readily be picked up by the keen observer in extraordinary proximity. The following diagram exhibits the local disposition of the immense nebulous neighbors north [actually south] of 88 Messier; they being preceded by M., No. 84 and followed by M. 58, 89, 90 and 91, in the same zone; thus describing a spot only 2 deg 1/2 from north to south, and 3 deg from east to west, as the micrometer shows it. And it will be convenient to keep in mind, that the situation of the extraordinary conglomerate of nebulae and compressed spherical clusters which crowd the Virgin’s left wing and shoulder, is pretty well pointed out to the practiced naked eye by Epsilon, Delta, Gamma, Eta, and Beta Virginis forming a semi-circle to the east, whilst due north of the last-mentioned star, Beta Leonis marks the north-west boundary. Reasoning upon the Herschelian principle, this may reverently be assumed as the thinnest or shallowest part of our firmament; and the vast laboratory of the segregating mechanism by which compression and insulation are ripened, in the course of unfathomed ages. The theme, however imaginative, is solemn and sublime.”
It’s about time! Enjoy this great spiral galaxy….
Top M88 image credit, Palomar Observatory courtesy of Caltech, M88 Hubble Image, M88 by Jim Quinn/Adam Block/NOAO/AURA/NSF, M88 by INGRID, and M88 image courtesy of NOAO/AURA/NSF.